When devices such as semiconductor devices and liquid crystal devices are manufactured by photolithography technique, a pattern of an original plate (hereinafter, also referred to as a mask) is conventionally transferred by photo exposure through a projection optical system to a photosensitive substrate (hereinafter, also referred to as a wafer) on which a photosensitive agent is applied.
In recent years, the devices have been more integrated, and fine processing technologies for the photosensitive substrate have accordingly been more developed. The fine processing technologies mainly use exposure apparatuses such as a mirror projection aligner, a stepper, and a scanner. The mirror projection aligner is an equal-magnification projection exposure apparatus configured to performing expose while scanning the original plate and the photosensitive substrate with an equal-magnification mirror optical system having an arc-shaped exposure region. The stepper is a reduction projection exposure apparatus configured to form a pattern image of the original plate on the photosensitive substrate by dioptric system and expose the photosensitive substrate by step-and-repeat system. The scanner is a reduction projection exposure apparatus configured to expose the photosensitive substrate while scanning the photosensitive substrate with synchronized scanning of the original plate.
The exposure is performed by overlapping a mask on a wafer. The exposure of the wafer with the stepper can cause alignment error, so-called overlay failure, due to multiple exposure shots. To prevent the overlay failure, many apparatuses and methods have been proposed.
Patent Document 1 proposes a projection exposure apparatus configured to align a mask pattern image with a certain region on a wafer every shot to form the mask pattern on the wafer, in which a wafer stage is moved to a predetermined position every shot by stepping movement. Patent Document 2 proposes a method for performing exposure after fine alignment every shot. In these documents, positions of the second and later shots are determined in accordance with a pattern position of the first shot. In practice, however, these techniques check a part of alignment marks and, if the checked mark is correctly positioned, omit alignment in the rest shots. Thus, there are problems of insufficient prevention of the overlay failure.
To solve such problems, Patent Document 3 proposes a method in which alignment is performed every one shot. This document proposes that the alignment is performed by die-by-die alignment. However, the alignment every one shot is complicated and thus has a problem of reduction in productivity.
In addition, these documents could not find out the cause of the overlay failure.